This invention relates to an optical system and device for demonstrating the effect of spherical aberration.
Various binocular devices, including two telescopes connected with a housing, are known. As an example, a conventional pair of binoculars is marked with terminology such as “10×42”. In this example, this terminology denotes that the diameter of the objective is Do=42 mm and that the angular magnification is M=10×. It also denotes that the exit pupil (diameter of rays entering the viewer eye) is De=Do/M=4.2 mm.
In this example of a typical binocular device, the binocular optics includes an objective lens with focal length f′o and an eyepiece lens with focal length f′e. The objective lens provides a real intermediate image of the distant object in the back focal plane of the objective. The eyepiece lens functions as a simple magnifier that the viewer uses to view the intermediate image. Between the objective lens and eyepiece lens there is typically a prism arrangement to invert the intermediate image so that the final image will not appear upside down to the viewer.
To adjust focus for closer objects or to accommodate for refractive errors of the viewer's eyes, the distance between the objective lens and the eyepiece lens can be adjusted by a wheel that affects the telescopes of both eyes simultaneously. There may also be an individual focus adjustment on the eyepiece of the right telescope, which can be used to compensate for anisometropia of the viewer but also to fine tune defocus in the altered telescope.
The objective lens is usually an achromatic doublet, or possibly an achromatic doublet coupled with a meniscus lens. The achromatic doublet lens is almost free of chromatic aberration, spherical aberration and coma when oriented correctly.
Various contact lenses are commercially available that adjust spherical aberration in order to improve visual acuity of the contact lens wearer. Additional examples of such lenses are described in U.S. Pat. No. 5,815,239 (Chapman et al.). In the illustrated examples in this patent, the optical zone of the contact lenses have a minus aberration value, by matching an appropriate shape factors for the anterior and posterior surfaces of the contact lens optical zones.